The invention relates to the catalytic codimerization of norbornadiene and phenylacetylenes or diphenylacetylenes. Particularly the invention relates to the preparation of an olefinic codimer of norbornadiene and phenylacetylenes or diphenylacetylenes using a specified catalyst system. Hydrogenation of either of the resulting olefinic codimers yields a saturated codimer having utility as a high energy fuel or a diluent for such fuels. The phenylacetylenes and diphenylacetylenes are referred to hereinafter collectively as PACE.
High energy fuel, which is often referred to as a high density fuel, can be used in either jet or rocket propulsion. Jet propulsion includes a jet engine which can be used for a missile plane and others and includes the three basic types, i.e., ramjet, turbo-jet and pulse jet. The term rocket generally refers to a device containing its own oxygen or oxidizing agent.
Norbornadiene is also known as bicyclo-(2.2.1) heptadiene-2,5. A method of preparation is disclosed in U.S. Pat. No. 2,875,256 issued Feb. 24, 1959. Hereinafter, norbornadiene is referred to as NBD. The latter can be represented by either one of the following structural formulas: ##STR2## NBD can be easily dimerized to an exo-exo hexacyclic dimer. Thus one problem in reacting NBD with another hydrocarbon reactant is to minimize the formation of the homodimer while encouraging the formation of the desired codimer.
The reaction of norbornenes and acetylenes without using a catalyst has been reported in J.C.S. Chem. Comm., 1976, pages 772-723, T. Mitsudo et al, in article titled "Ruthenium-catalyzed [2+2] Cross addition of Norbornene Derivatives and Dimethyl Acetylene dicarboxylate". Such reactions are also reported in Tetrahedron, 1966, M. Hara et al, "Photo-Addition-Reactions of Dimethyl Maleate and Dimethyl Acetylene Dicarboxylate with Norbornene". A. Carbonaro, et al in Tetrahedron Letters, 49, 1965, pages 5129-5130 in "Oligomerization Catalysts-IV., Formation of Benzene Derivatives by Catalytic Reaction Between Norbornadiene and Acetylenic Hydrocarbons; A core of Catalyzed Inverse Diels-Alder Reaction", reports on the formation of aromatic compounds in the presence of iron catalysts. T. Sasaki et al in an article in the J. Org. Chem., Vol. 37, No. 14, 1972, titled "Studies on Reactions of Isoprenoids" reports on reactions of norbornadiene with unsymmetrically substituted acetylenic and heterodienophiles in the absence of a catalyst. Schrauzer et al in an article titled "Catalytic Addition of Olefins and Alkynes to Norbornadiene with Ni.sup.0 Compounds and a New Ni.sup.II complex as Catalyst", in Jahrg. 97, 1964, pages 2451-2462, reports on reactions or norbornadiene with diphenylacetylene or acetylene.